The invention relates to an improved method for winding conical cross-wound bobbins and a device for carrying out said method.
In a known method according to DE-OS-3 123 494, which corresponds with U.S. Pat. No. 4,501,116, a centering spindle is used during thread attachment, which spindle displaces the thread supplied with the aid of draw-off rollers to the end of the bobbin with the larger diameter, the bobbin being driven during thread attachment by means of an auxiliary drive roller. Since there is a marked difference between the circumferential velocity at each bobbin end and the circumferential velocity in the longitudinal center of the bobbin where the bobbin or empty casing is driven, in particular on account of the conicity of the bobbin or empty casing, it is customary to reduce the drive velocity of the bobbin or empty casing during thread attachment by an average of 2%. In this respect it is assumed that the thread is wound onto the end of the empty casing with the larger diameter. However, this general reduction in the bobbin drive velocity does not correspond to the differences in velocity which actually occur, so that thread breaks or rough handling of the thread will take place. The same applies to a thread attachment phase in which the thread can also be selectively wound onto the end of the bobbin or empty casing with the smaller diameter, the circumferential velocity then being too slow for a perfect thread uptake.
According to DE-OS-2 242 151, which corresponds with U.S. Pat. No. 3,938,306, an intermediate store is provided for the thread, which store compensates differences in velocity the size of the thread length stored being controlled by driving the bobbin or empty casing at varying speeds.
In DE-OS-2 458 853, which corresponds with U.S. Pat. No. 4,0899,480, the use of a plurality of drive rollers is proposed, which are distributed axially along the length of the bobbin and which are driven in succession synchronously with the movement of the shifting thread guide so as to wind the thread with substantially constant tension.
However, the methods mentioned above do not take into account the actual circumstances which result during thread attachment in the case of different bobbin conicities and different bobbin outer diameters.
It is the object of the invention to provide a method and a device in order to rule out the possibility of thread breaks or unevenness during winding in connection with thread attachment.
According to the invention, this object is attained through practice of the presently disclosed method and devices.
When reference is made to the conicity or the velocity of the bobbin, then according to the invention this is also understood to include the empty casing, onto which no thread has yet been wound.
The actual outer diameter of the bobbin is the value from which it is possible, provided that the conicity of the bobbin is known, to precisely determine the differences in circumferential velocity occuring between the longitudinal center of the bobbin and the bobbin ends during bobbin change-overs or thread attachments. In this connection, said actual outer diameter can be selectively determined at the large or small diameter or centrally between the two bobbin ends. As a result of the fact that the drive velocity of the bobbin is altered relative to the operating velocity as a strict function of the determined actual outer diameter, the thread approaching with the predetermined supply velocity runs correctly onto the bobbin, so that on the one hand thread breaks as a result of excessive thread tension and on the other hand uneveness in the winding pattern as a result of the low thread tension are reliably avoided. In this connection, it is advantageous during bobbin change-overs or thread attachments for the thread to be wound on unchanged with the respective adjustment supply velocity, so that the spinning process does not have to be unnecessarily interrupted or changed over.
In this respect, the present exemplary method of throttling operation is expedient, since the throttling of the drive velocity relative to the operating velocity as a function of the actual outer diameter of the bobbin corresponds exactly to the actual conditions, which leads to a considerably improved winding quality as compared with the known method with a general reduction of the drive velocity. The changes in the drive velocity effected strictly as a function of the determined actual outer diameter of the bobbin or empty casing allow thread attachments at high thread speeds. In such throttling operations, preferably the drive velocity during the winding of the thread at the end of the bobbin with the larger diameter is throttled relative to the operating speed as a function of the actual outer diameter.
In practice, the present exemplary method of operation of changing the drive velocity by up to 15 percent relative to the operating velocity has proved particularly expedient. The change in the drive velocity is carried out within this defined range of up to 15%. The change becomes smaller the larger the outer diameter of the bobbin and the slighter the conicity of the bobbin.
A further important present measure is that the actual central outer diameter of the diameter of the bobbin or empty casing is determined, transmitted by data transfer to the control unit, and evaluated there to determine the degree of required change in the drive velocity. The actual central outer diameter is the easiest value to determine using the method and device according to the invention. From the value of the actual central outer diameter it is possible to precisely determine the differences in velocity which result over the length of the bobbin between the bobbin ends. Data transmission is an error-free, sufficiently quick and therefore extraordinarily precise method, which is particularly suited to this type of problem. The evaluation and conversion of the determined values into the change in drive velocity is carried out in conventional manner using one or more microprocessors.
A further expedient method of operation is presently disclosed, in which, for the thread attachment, the bobbin held by bobbin carrier arms is swung out of the operating position into a predetermined bobbin release position. From the degree to which the bobbin is swung out or the time taken for the pivoting movement of the bobbin carrier arms from the operating position into the bobbin release position, the actual outer diameter can be precisely determined, components advantageously being used which are necessary anyway for the operation of the device.
A further expedient method of operation is presently disclosed, in which, for the thread attachment, an auxiliary drive roller can be moved from a passive position to abut against the circumference of the bobbin or empty casing. Here too, the degree of or time taken for the movement of the auxiliary drive roller between the predetermined passive position and its abutment against the bobbin or empty casing circumference allows for a precise determination of the actual outer diameter of the bobbin or empty casing.
Another variation of the method, in which the thread spinning length is constantly determined and stored, is presently disclosed. The respective thread spinning length of each spinning station is stored in a control unit in the machine control room. Deviations caused by the material of the thread only have an effect in the case of larger bobbin outer diameters. However, since in the case of larger bobbin outer diameters the differences between the circumferential velocity at the longitudinal center of the bobbin and the bobbin ends become smaller, the material-related deviations are then also compensated for.
Presently disclosed devices are particularly suitable for carrying out the present method, in which are provided a bobbin, which is driven by a drive device, and a control unit, which is connected in respect of velocity control with the drive device for the bobbin. Sensors or light barriers are actuated successively over the increasing outer diameter of the bobbin, so that they are in a position to precisely inform the control unit of the actual outer diameter. Sensors or light barriers of this type are operationally reliable and can be accommodated in a space-saving manner.
Another embodiment of the device is presently disclosed, which device comprises a bobbin and the pivotable bobbin carrier arms, which support the bobbin and which can be pivoted during thread attachment to a degree related to the actual outer diameter of the bobbin into a bobbin release position. In an advantageous manner, components which are already contained in the device are used for determining the actual outer diameter. In this connection, it is not necessary in order to determine the actual outer diameter to enter into the direct area of movement of the bobbin. The actual outer diameter is precisely determined at a point at a distance from the bobbin. In this respect, a potentiometer-based embodiment of the device as presently disclosed has proved expedient in practice. A potentiometer or a timing circuit are components which operate reliably, are dirt-resistant, are compact and produce good, usable signals.
A further, alternative embodiment of the device is also presently disclosed, in which an auxiliary drive roller is provided for driving the bobbin during thread attachment, which roller can be pivoted between a predetermined passive position and a drive position on the bobbin circumference dependent upon the actual outer diameter, the auxiliary drive roller being connected with a drive device controlled by the control unit. In this case too, the measuring device is used which is at a distance from the area of movement of the bobbin, so that the respective actual outer diameter can be determined and transmitted to the control unit using components which are necessary anyway for the operation of the device.
Finally, another presently disclosed embodiment of the device according to this invention is also expedient, in which a control unit is provided, which is in connection with draw-off rollers supplying the thread and with a drive device for the bobbin and comprises a computer component which constantly determines and stores the thread spinning length. Since the control unit is informed of the thread spinning length anyway, it requires no significant additional cost to extend the computer component so that it determines the actual outer diameter of the bobbin during thread attachment from predetermined and stored values relating to the thread spinning length and places the control unit in a position to impart the necessary change in velocity for the drive device.